Three-dimensional (3-D) imaging is needed for many applications including robotic vision, inspection, navigation, collision avoidance, target recognition and aimpoint refinement for munitions. Conventional 3-D imaging, which utilizes a scanned laser source and a detector that measures return signals pixel by pixel, is too slow for many of the above applications. To increase the speed of data collection, scannerless range imaging (SRI) has been introduced to illuminate a scene of interest all at once using multiple illumination pulses or continuous modulation of the illumination, and then to collect the data wherefrom a 3-D image can be constructed in a parallel fashion (see e.g. U.S. Pat. Nos. 4,935,616 and 6,088,086 which are incorporated herein by reference). As it is currently practiced, SRI requires a minimum of three illumination pulses to obtain sufficient information to construct a 3-D image. For many of the above applications, especially when the scene of interest is rapidly changing over time or when the SRI system is moving, the range information for the 3-D image can be distorted requiring the use of signal correction techniques.
What is needed is a 3-D imaging system that is capable of producing a 3-D image of a scene of interest using a single pulse of light, and which can acquire subsequent 3-D images of the scene with each additional pulse of light. Such a 3-D imaging system would largely eliminate any image distortion due to movement since the movement will generally be very small over the time scale of the single pulse of light which can be subnanosecond or up to a few tens of nanoseconds. Additionally, such a 3-D imaging system should be adaptable in certain embodiments for continuous imaging (e.g. by using a repetitively pulsed or modulated light source).
The present invention provides a solution to 3-D imaging using a single pulse of light by providing a two-dimensional (2-D) array of photodetectors with associated circuitry that operates to process a detected light signal from each photodetector in parallel by sharing the detected light signal between multiple components which can simultaneously process the detected light signal to generate intensity and range information for each photodetector that can then be used to construct a 3-D image of a scene. The use of parallel information processing according to the present invention represents an advance over the prior art by reducing the number of required pulses from the light source to a single pulse at a minimum, thereby allowing essentially instantaneous 3-D imaging (also termed flash ladar imaging). The present invention can further be used with a modulated light source to provide continuous imaging at a video rate.
These and other advantages of the present invention will become evident to those skilled in the art.